1. Field of the Invention
The present invention relates to a system interconnection electric power generator for enabling regeneration (supply) of electric power generated therein to a commercial power supply system which is interconnected to the electric power generator, and a method of controlling the system interconnection electric power generator.
2. Description of the Related Art
Recently, there has been recently becoming widespread a solar energy generator (photovoltaic generator) as a system interconnection electric power generator in which not only electric power generated by utilizing sunlight as an energy source is supplied for personal use, but also extra electric power thus generated (which has not been used for personal use) is regenerated (supplied) to a commercial power supply system.
In such a solar energy generator, DC power generated by using a solar battery is boosted by a boosting circuit and then the DC power thus boosted is converted to AC power corresponding to the AC power of a commercial power supply system by using an inverter circuit.
In such a solar energy generator as described above, the DC power generated by the solar battery is used as a power supply source for various kinds of equipment constituting the solar energy generator, such as a boosting circuit, an inverter circuit, a controller for controlling the boosting circuit and the inverter circuit, various types of detecting sensors, etc.
Further, according to the solar energy generator thus constructed, in order to enhance the safety of the solar energy generator thus constructed, a current sensor for detecting the earth fault of DC power supplied to various kinds of equipment is equipped to DC lines at the solar battery side. A current converter or the like is generally used as the current sensor, and it contains a magnetic member around which a coil is wound. The magnetic member of the current sensor is generally formed of expensive super-saturated reactor or the like.
In such a solar energy generator as described above, since electric power is generated by using sunlight, the amount of electric power to be generated by using a solar battery is reduced under such an atmosphere that the amount of insolation is low. For example, this is liable to occur at sunset or the like. Particularly in such a case that the electric power generated by the solar battery is partially supplied as a power supply source to various kinds of equipment constituting the solar energy generator, that is, a part of the electric power generated by the solar battery is consumed at these kinds of constituent equipment, the level of electric power to be supplied (regenerated) from the solar energy generator to the commercial power supply system is lower than a specified level required for the commercial power supply system at sunset or the like. Consequently, the supply of the electric power from the solar energy generator to the commercial power supply system must be stopped, that is, the operation of the solar energy generator itself must be stopped.
Therefore, the controller of the solar energy generator judges at all times whether the amount of electric power generated by the solar energy generator is lowered to the extent that it is impossible to use the electric power thus generated for the commercial power supply system at sunset or the like, that is, whether the electric power generated in the solar energy generator is lower than the specified power level or not, and stops the operation of the solar energy generator on the basis of the above judgment. In such a case that the amount of electric power generated in the solar energy generator is lower than the specified level, the electric power to be supplied from the solar energy generator to the various kinds of equipment (containing the controller) constituting the solar energy generator is also reduced, and thus the operation of these constituent equipment is unstable. Particularly when the electric power to be supplied to the controller (control power supply source) is lower, the controller cannot surely perform the judgment as to the reduction of the electric power (i.e., sunset or the like).
Furthermore, in such a solar energy generator as described above, the operational status of the solar energy generator under operation is merely displayed on a display panel or the like at that time point. Accordingly, in such a case that for example when some abnormality occurs in the commercial power supply system, the solar energy generator carries out a protecting operation of stopping supply of electric power therefrom to the commercial power supply under abnormality in order to protect the commercial power supply from being damaged or the like by further supply of the electric power to the commercial power supply, the data on the protecting operation of the solar energy generator are merely displayed on the display panel or the like at the time point when the abnormality occurs. That is, the data of the protecting operation which has been carried out until the abnormality is fixed do not remain.
Accordingly, after such a protecting operation is finished, even the fact that the protecting operation is carried out is not left. In this case, a service man(woman), a maintenance man(woman) or the like must take a countermeasure to the lack of the electric power to be supplied from the solar energy generator to the commercial power supply system while paying his/her attention to only the integration value of the amount of electric power generated by the solar energy generator. Therefore, it is substantially impossible to take a proper countermeasure to the lack of the electric power to be supplied from the solar energy generator to the commercial power supply system. That is, it has been hitherto impossible to determine the accurate cause for the lack of the electric power to be supplied from the solar energy generator to the commercial power supply system, and take the proper countermeasure thereto.
Therefore, the present invention has been implemented in view of the foregoing situation, and has a first object to provide a system interconnection electric power generator that can always secure electric power to be supplied to various kinds of equipment of the system interconnection electric power generator, such as control electric power to be supplied to a controller, until the operation of the system interconnection electric power generator is finished, and a method of controlling the system interconnection electric power generator.
A second object of the present invention is to provide a system interconnection electric power generator that can surely judge the operational status thereof and properly perform maintenance and troubleshooting, and a method of controlling the system interconnection electric power generator.
A third object of the present invention is to provide a system interconnection electric power generator that can detect the earth fault of direct current thereof at low cost and ensure high safety, and a DC earth fault detecting device used for the system interconnection electric power generator.
In order to attain the above objects, according to a first aspect of the present invention, a system interconnection electric power generator having various kinds of equipment for generating electric power and supplying the electric power to a commercial power supply system electrically-connected thereto, is characterized by comprising: an electric power generator for generating DC power; a boosting circuit for boosting the DC power generated in said electric power generator; an inverter circuit for converting the DC power boosted in said boosting circuit to AC power; a controller for controlling at least said boosting circuit and said inverter circuit; and a power source switching device that is controlled by said controller so as to select one of said electric power generator and the commercial power supply system as a power source for the power to be supplied to the various kinds of equipment of said system interconnection electric power generator.
In the system interconnection electric power generator, the AC power of the commercial power supply is rectified by the inverter circuit and then supplied to the various kinds of equipment of the system interconnection electric power generator.
In the system interconnection electric power generator, the electric power generator comprises a solar battery for generating the electric power corresponding to the amount of sunlight received.
In the system interconnection electric power generator, the power source switching device selects the electric power generator as the power source to supply the electric power generated by the electric power generator to the various kinds of equipment of the system interconnection electric power generator when the electric power generated by the electric power generator exceeds a predetermined level, and selects the commercial power supply system as the power source to supply the AC power of the commercial power supply system to the various kinds of equipment of the system interconnection electric generator when the electric power generated by the electric power generator is not more than the predetermined level.
In the system interconnection electric power generator, the controller intercepts the electrical connection between the various kinds of equipment of the system interconnection electric power generator and the commercial power supply system when the operation of the system interconnection electric power generator is finished.
According to a second aspect of the present invention, a system interconnection electric power generator having various kinds of equipment for generating electric power and supplying the electric power to a commercial power supply system electrically-connected thereto, is characterized by comprising: an electric power generator for generating DC power; a boosting circuit for boosting the DC power generated in the electric power generator; an inverter circuit for converting the DC power boosted in the boosting circuit to AC power; a controller for controlling at least the boosting circuit and the inverter circuit; and a power source switching device that is controlled by the controller so as to select one of the electric power generator and the commercial power supply system as a power source for the power to be supplied to the controller of the system interconnection electric power generator.
According to a third aspect of the present invention, a system interconnection electric power generator having various kinds of equipment for generating electric power and supplying the electric power to a commercial power supply system electrically-connected thereto, is characterized by comprising: an electric power generator for generating DC power; a boosting circuit for boosting the DC power generated in the electric power generator; an inverter circuit for converting the DC power boosted in the boosting circuit to AC power; a controller for controlling at least the boosting circuit and the inverter circuit; and a storage device that is controlled by the controller so as to store operational status data of the system interconnection electric power generator under operation.
In the system interconnection electric power generator, the operational status data are data on a protecting operation of protecting the system interconnection electric power generator or the commercial power supply system.
In the system interconnection electric power generator, the controller controls the storage device to store the operational status data of the system interconnection electric power generator under operation while keeping the power to be supplied to the controller just before the operation of the system interconnection electric power generator is finished.
In the system interconnection electric power generator, the electric power generator comprises a solar battery for generating the electric power corresponding to the amount of sunlight received.
In the system interconnection electric power generator, the controller controls the various kinds of equipment of the system interconnection electric power to keep the power to be supplied to the controller when the amount of insolation is reduced to a predetermined level or less, and stores the operational status data of the system interconnection electric power generator under operation into the storage device under the state that the power to be supplied to the controller is kept.
In the system interconnection electric generator, the controller makes a judgment as to sunset while keeping power required to the operation of said controller, and stops the supply of the power to the commercial power supply system when the judgment on sunset is affirmative.
According to a fourth aspect of the present invention, a method of controlling a system interconnection electric power generator comprising an electric power generator for generating DC power, a boosting circuit for boosting the DC power generated in the electric power generator, and an inverter circuit for converting the DC power boosted in the boosting circuit to AC power, the AC power thus boosted being supplied to a commercial power supply system, is characterized in that data representing an operational status of the system interconnection electric power generator under operation are stored in a storage device.
In the method, the operational status data is data on a protecting operation of protecting the system interconnection electric power generator or the commercial power supply system.
In the method, the operational status data of the system interconnection electric power generator under operation are stored in the storage device while keeping control power for a controller of the system interconnection electric power generator just before the operation of said system interconnection electric power generator is stopped.
In the method, the operational status data of the system interconnection electric power generator is stored in the storage device while keeping control power for a controller of the system interconnection electric power generator when the amount of insolation is reduce to a predetermined level or less.
In the method, a judgment on sunset is made under the state that control power for a controller of the system interconnection electric power generator is kept, and if the judgment on sunset is affirmative, the supply of the power to the commercial power supply system is stopped.
According to a fifth aspect of the present invention, a system interconnection electric power generator having various kinds of equipment for generating electric power and supplying the electric power to a commercial power supply system electrically-connected thereto, is characterized by comprising: an electric power generator for generating DC power; a boosting circuit for boosting the DC power generated in the electric power generator; an inverter circuit for converting the DC power boosted in the boosting circuit to AC power; a controller for controlling at least the boosting circuit and the inverter circuit; plural DC lines connected between the electric power generator and the boosting circuit so that direct current achieved in the electric power generator flows through the plural DC lines; and a DC earth fault detector for measuring the difference in current between the plural DC lines extending from the electric power generator to detect whether DC earth fault occurs or not in said system interconnection electric power generator, wherein the DC earth fault detector comprises a current sensor disposed on the plural DC lines, and the current sensor has a detecting core formed of a zero current transformer (ZCT).
In the system interconnection electric power generator, a magnetic member of the zero current transformer around which a coil is wound is formed of permalloy.
In the system interconnection electric power generator, the current sensor is disposed so that the DC lines penetrate through the detecting core of the current sensor, the detecting core is kept under an excited state so that the difference in flowing current between the DC lines can be measured, and it is judged on the basis of the output from the detecting core whether DC earth fault occurs in the DC lines.
In the system interconnection electric power generator, the electric power generator comprises a solar battery for generating the electric power corresponding to the amount of sunlight received.
According to a sixth aspect of the present invention, a DC earth fault detecting device is characterized by comprising: a current sensor disposed on plural measurement target conductors through which direct current flows; and a detector for measuring the difference in flowing current between the plural measurement target conductors and detects on the basis of the measurement result whether DC earth fault occurs in the plural measurement target conductors, wherein the current sensor having a detecting core formed of a zero current transformer (ZCT).
In the DC earth fault detecting device, the current sensor is disposed so that the DC lines penetrate through the detecting core of the current sensor, the detecting core is kept under an excited state so that the difference in flowing current between the DC lines can be measured, and it is judged on the basis of the output from the detecting core whether DC earth fault occurs in the DC lines.